Searching for New Physics Through AMO Precision Measurements

We briefly review recent experiments in atomic, molecular, and optical physics using precision measurements to search for physics beyond the Standard Model. We consider three main categories of experiments: searches for changes in fundamental constants, measurements of the anomalous magnetic moment of the electron, and searches for an electric dipole moment of the electron.Comment: Prepared for Comments on AMO Physics at Physica Script

A Stochastic Approach to Chemical Evolution

Observations of elemental abundances in the Galaxy have repeatedly shown an intrinsic scatter as a function of time and metallicity. The standard approach to chemical evolution does not attempt to address this scatter in abundances since only the mean evolution is followed. In this work the scatter is addressed via a stochastic approach to solving chemical evolution models. Three standard chemical evolution scenarios are studied using this stochastic approach; a closed box model, an infall model, and an outflow model. These models are solved for the solar neighborhood in a Monte Carlo fashion. The evolutionary history of one particular region is determined randomly based on the star formation rate and the initial mass function. Following the evolution in an ensemble of such regions leads to the predicted spread in abundances expected, based solely on different evolutionary histories of otherwise identical regions. In this work 13 isotopes are followed including the light elements, the CNO elements, a few $\alpha$-elements, and iron. It is found that the predicted spread in abundances for a 10^5\Msun region is in good agreement with observations for the $\alpha$-elements. For CN the agreement is not as good perhaps indicating the need for more physics input for low mass stellar evolution. Similarly for the light elements the predicted scatter is quite small which is in contradiction to the observations of \He{3} in \hii\ regions. The models are tuned for the solar neighborhood so good agreement with \hii\ regions is not expected. This has important implications for low mass stellar evolution and on using chemical evolution to determine the primordial light element abundances in order to test big-bang nucleosynthesis.Comment: 34 pages + 16 figures included with epsf and rotate styles, LaTeX2.09. Also available from ftp://astro.uchicago.edu/pub/astro/copi/chem

Evolution of Deuterium, 3He and 4He in the Galaxy

In this work we present the predictions of the ``two-infall model'' concerning the evolution of D, 3He and 4He in the solar vicinity, as well as their distribution along the Galactic disk. Our results show that, when adopting detailed yields taking into account the extra-mixing process in low and intermediate mass stars, the problem of the overproduction of 3He by the chemical evolution models is solved. The predicted distribution of 3He along the disk is also in agreement with the observations. We also predict the distributions of D/H, D/O and D/N along the disk, in particular D abundances close to the primordial value are predicted in the outer regions of the Galaxy. The predicted D/H, D/O and D/N abundances in the local interstellar medium are in agreement with the mean values observed by the Far Ultraviolet Spectroscopic Explorer mission, although a large spread in the D abundance is present in the data. Finally, by means of our chemical evolution model, we can constrain the primordial value of the deuterium abundance, and we find a value of (D/H)_p < 4 10(-5) which implies Omega_b h^2 > 0.017, in agreement with the values from the Cosmic Microwave Background radiation analysis. This value in turn implies a primordial 4He abundance Y_p > 0.244.Comment: 21 pages, 10 figures, accepted for publication in Astronomy & Astrophysics (minor proof corrections + corrections in Table 6, Figs.8 and 9